Moving tests into CpsScripTest class as that's what this is really testing
parsed CpsScript needs to go through a proper initialization treatment
Pushed the logic necessary to run CpsScript to CpsGroovyShell

I think this keeps various code that calls GroovyShell.evaluate() most
clean
Testing the return value
Renamed to the "load" step
Fix up for the rename
Record loaded scripts and resurrect them when coming back from the persisted state.
For this "readResolve()" method to work it needs to be protected.

See org.jboss.marshalling.reflect.SerializableClass
Testing the load() script that involves persistence of loaded programs